This invention is related to a vehicle security device, and more particularly to a vehicle security system for a vehicle provided with a PWM interior light delay without being mistriggered.
Vehicle security systems are widely used to deter vehicle theft, prevent theft of valuables from a vehicle, deter vandalism, and to protect vehicle owners and occupants. A typical automobile security system, for example, includes a central processor or controller connected to a plurality of vehicle sensors. The sensors, for example, may detect opening of the trunk, hood, doors, windows, and also movement of the vehicle or in the vehicle. Ultrasonic and microwave motion detectors, vibration sensors, sound discriminators, differential pressure sensors, and switches may also used as sensors. In addition, radar sensors may be used to monitor the area proximate the vehicle. The controller also typically operates to give an alarm indication in the event of triggering of a vehicle sensor. The alarm indication may typically be a flashing of the lights and/or the sounding of the vehicle horn or a siren. In addition, the vehicle fuel supply and/or ignition power may be selectively disabled based upon an alarm condition.
A typical security system also includes a receiver associated with the central processor or the controller that cooperates with one or more remote transmitters typically carried by the user as disclosed, for example, in U.S. Pat. No. 4,383,242. The remote transmitter may be used to arm and disarm the controller in the vehicle or provide other remote control features from a predetermined range outside the vehicle.
As mentioned above, the vehicle security system must be connected to the signal lines of door switches to detect whether the doors are opened illegally so as to trigger the vehicle security system for achieving the purpose of protecting the vehicle. Now, most of the vehicles are provided with the interior light delay, which is convenient for the drivers and passengers. The delay of the interior light is connected to the signal lines of door switches, and thus the interior light will not be extinguished immediately when all doors are closed. Controlled by the interior light delay, the interior light will be delayed to extinguish for a predetermined time such as 10 or 15 seconds. Normally, the interior light delay is a pulse width modulation (PWM), which outputs a voltage pulse signal with width modulation to the interior light of the vehicle such that the interior light is extinguished gradually. FIG. 2a discloses a typical circuit of a PWM interior light delay connecting to a vehicle security system controller, wherein the PWM interior light delay can be positively or negatively triggered. FIG. 2b discloses a voltage pulse signal with width modulation outputted by the PWM interior light delay of negatively triggered type, wherein the interior light will be a open circuit if the output voltage pulse signal is high, and the interior light will be a short circuit if the output voltage pulse signal is low. The modulation width of the voltage pulse signal of the PWM interior light delay increases gradually, and eventually the voltage pulse signal maintains a stable state of high potential such that the interior light is delayed to extinguish gradually for a predetermined time. For the PWM interior light delay of the positively triggered type, the interior light will be a short circuit if the output voltage pulse signal is high, and the interior light will be a open circuit if the output voltage pulse signal is low. The modulation width of the voltage pulse signal of the PWM interior light delay increases gradually, and eventually the voltage pulse signal maintains a stable state of low potential such that the interior light is delayed to extinguish gradually for a predetermined time.
For the installation of the vehicle security system, the door detective signal lines of the security system are normally connected to the output end of the PWM interior light delay. When all of the doors are closed, the PWM interior light delay outputs a voltage pulse signal with width modulation so as to extinguish the interior light gradually. However, as the security system are connected to the output end of the PWM interior light delay, when all of the doors are closed and the door detective signal line receives the voltage pulse signal of the PWM interior light delay, the vehicle security system will misjudge that at least one of the doors is illegally opened and thus be mistriggered to actuate alarm indication, such as a flashing of the lights and/or the sounding of the vehicle horn or a siren. Therefore, this mistrigger of the vehicle security system causes a inconvenient problem to the users. For avoiding the mistrigger of the vehicle security system, the door detective signal lines of the vehicle security system are connected directly to the door switches respectively. However, for such installing method, it is very difficult to find out the position of the door switches and the installation may take much time. Alternatively, a predetermined bypass period, such as twenty (20) seconds, is set for the vehicle security system not to detect the PWM signal of the doors when the vehicle security system is initially armed so as to avoid the undesirable mistrigger. However, various vehicles have various interior light delay time. When the predetermined bypass period is shorter than the interior light delay time, the vehicle security system still might be mistriggered.
For the above-mentioned disadvantages of the prior vehicle security system, there has been a need existing for a vehicle security system for the vehicle provided with a PWM interior light delay in which the vehicle security system would not be mistriggered due to the PWM interior light delay so as to overcome the disadvantages of the prior art.
It is a primary object of the present invention to provide a vehicle security system for a vehicle with a PWM interior light delay, wherein the vehicle security system would not be mistriggered.
It is another object of the present invention to provide a vehicle security system for a vehicle with a PWM interior light delay, wherein the installation of the vehicle security system is easy and timesaving.
In order to achieve these objects, the vehicle security system according to the present invention mainly includes a control unit having a central processor unit or microprocessor, a receiver which is connected to the microprocessor for receiving a signal from a remote transmitter. The control unit also comprises an input interface and an output interface, wherein the input interface is connected to various vehicle sensors and the output interface is connected to various vehicle security devices. A PWM interior light delay is disposed between the door sensors and the input interface to provide a voltage pulse signal with width modulation for a vehicle interior light such that the interior light is extinguished gradually for a predetermined time.
According to this vehicle security system of the present invention, the user can selectively set the vehicle security system whether the vehicle is provided with the PWM interior light delay. When the vehicle security system enters the security armed state, the vehicle security system will check whether the last closed time of the door switches exceeds a predetermined time (such as 3 seconds). If the last closed time exceeds the predetermined time, the alarm would be triggered; if the last closed time dose not exceed the predetermined time, the alarm would not be triggered such that the vehicle security system will not be mistriggered. Therefore, when all of the door are closed and the PWM interior light delay outputs a voltage pulse signal with width modulation to extinguish the interior light gradually, the vehicle security system according to the present invention will not be mistriggered and the user will not be annoyed. Moreover, since the vehicle security system of the present invention for a vehicle with a PWM interior light delay is directly connected to the output end of the PWM interior light delay, the installation of the vehicle security system is easy and timesaving.